RATIONALE: Monoclonal antibodies, such as trastuzumab, can block tumor growth in different ways. Some block the ability of tumor cells to grow and spread. Others find tumor cells and help kill them or carry tumor-killing substances to them. It is not yet known whether giving trastuzumab for 6 months is as effective as giving trastuzumab for 1 year in treating patients with breast cancer.

PURPOSE: This randomized phase III trial is studying trastuzumab to see how well it works when given for 6 months compared to 12 months in treating women with nonmetastatic breast cancer that can be removed by surgery.

Arm I (control arm, 12-month therapy): Patients continue to receive trastuzumab (Herceptin®) IV until a total of 12 months of therapy is completed in the absence of disease progression or unacceptable toxicity.

Arm II (experimental arm, 6-month therapy): Patients continue to receive trastuzumab* IV until a total of 6 months of therapy is completed in the absence of disease progression or unacceptable toxicity.

NOTE: *Patients who have already finished 6 months of trastuzumab at randomization do not receive further trastuzumab.

After completion of study therapy, patients are followed periodically for approximately 5 years.

PROJECTED ACCRUAL: A total of 7,000 patients will be accrued for this study.

Eligibility

Ages Eligible for Study:

18 Years and older

Genders Eligible for Study:

Female

Accepts Healthy Volunteers:

No

Criteria

DISEASE CHARACTERISTICS:

Histologically confirmed adenocarcinoma of the breast

Nonmetastatic disease

Positive or negative axillary nodes

Tumor size ≥ 10 mm

Resectable disease

Must have received ≥ 4 courses of chemotherapy for this disease

A 12-month adjuvant treatment with trastuzumab (Herceptin®) has been initiated

Informed consent form must be signed between the third and sixth months of trastuzumab therapy

Overexpression of HER-2 in the invasive component of the primary tumor as indicated by 1 of the following:

3+ by immunohistochemistry (IHC)

2+ by IHC and confirmation by fluorescent in situ hybridization (FISH) or chromogenic in situ hybridization (CISH)

Hormone receptor status not specified

PATIENT CHARACTERISTICS:

Female

Menopausal status not specified

LVEF considered favorable for continuing trastuzumab treatment as measured by echocardiography or MUGA at 2-4 months after beginning adjuvant trastuzumab

No serious cardiac illness or medical condition precluding trastuzumab treatment, including any of the following:

History of documented congestive heart failure

High-risk uncontrolled arrhythmias

Angina pectoris requiring antianginal medication

Severe dyspnea at rest or oxygen-dependent

No known hypersensitivity to trastuzumab, murine proteins, or any of the excipients

Not pregnant or nursing

No social, geographical, or psychological condition that would preclude study participation

PRIOR CONCURRENT THERAPY:

See Disease Characteristics

Other prior anti-HER-2 therapy allowed

No prior trastuzumab other than initiation of trastuzumab adjuvant therapy

Contacts and Locations

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study.
To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below.
For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT00381901